ABSTRACT
Objectives: The main objective of this study was to determine the vitamin A (VA) bioefficacy of high β-carotene, biofortified (orange) maize in Zambian preschool children. Methods: A randomized, placebo-controlled orange maize efficacy trial was conducted in rural Zambian children (n = 140, 71.5±6.9 months). The paired 13C-retinol isotope dilution test, the most sensitive indirect marker of VA status, was used to measure total body reserves (TBR) of VA before and after a 90-d intervention. Treatment arms were white maize with placebo oil (VA-), white maize with 400 μg (VA+), and orange maize with placebo oil (orange). Results: TBR of VA increased in the VA+ and orange groups (203±386 and 109±341 μmol, respectively) (P = 0.0034), and were different from the VA- group (-4.5±208 μmol) using nonparametric analysis. Medians were VA- 12.6, VA+ 97.8, orange 83.7 μmol. Baseline estimates of liver concentration were 1.13±0.41 μmol/g, with 59% >1 μmol/g, the current sub-toxicity cutoff; none were <0.1 μmol/g, the proposed cutoff for deficiency. The bioconversion factor was 10.4 μg β-carotene: 1 μg retinol using the middle three quintiles of change in TBR from each treatment group. Serum retinol concentrations did not respond (P = 0.16). Conclusions: Biofortified maize is a very effective VA source when consumed as a staple food and could avoid potential toxicity issues with preformed VA from supplementation or fortification programs as observed in this population. Stable isotope methodology should be used to elucidate VA status of various populations, and serum retinol should be used with caution in setting global health policy.